Seminar

Exchange of debris between planetary systems

Abstract

The exchange of meteorites among the terrestrial planets of our Solar System is a well established phenomenon. Similarly, could solid material be transferred between planetary systems? We examine a dynamical process that yields very low escape velocities using nearly parabolic trajectories, and the reverse process that allows for low velocity capture. These processes are chaotic and provide a mechanism for minimal energy transfer that yield an increased transfer probability compared to that of previously studied mechanisms that have invoked hyperbolic trajectories. However, they require a small relative velocities and would therefore be applicable when the stars are still embedded in their maternal cluster. We estimate the transfer probability in a stellar cluster as a function of stellar mass and cluster size. We find that significant amounts of solid material could potentially have been transferred from the early Solar System to our nearest neighbor stars in the cluster.
Regarding the exchange of km-size debris today, given the high relative velocities between the Sun and its neighbors, any incoming extra-solar debris would be identified as a hyperbolic comet. No hyperbolic comet has been observed so far, but future surveys with Pan-STARRS and LSST will provide wide coverage maps of the sky to a very high sensitivity ideal to detect moving objects. In anticipation of these observations, we estimate the number of extrasolar comets that might be detected taking into account recent results on the frequency of planetesimal and planet formation (from debris disks and planet surveys), the amount of solid material that might be available to form planetesimals (from protoplanetary disks studies), and the size distribution of planetesimals (from the study of the small body population in the Solar System).